2021-2022学年固体地球物理研究生 学术报告（论坛）第一期

报告一：Low-frequency earthquakes are a series of recurring small earthquakes that are thought to compose tectonic tremors. Compared with regular earthquakes of the same magnitude, low-frequency earthquakes have longer source durations and smaller stress drops and slip rates. The mechanism that drives their unusual type of stress accumulation and release processes is unknown. Here, we use phase diagrams of rupture dynamics to explore the connection between low-frequency earthquakes and regular earthquakes. By comparing the source parameters of low-frequency earthquakes from 2001 to 2016 in Parkfield, on the San Andreas Fault, with those from numerical simulations, we conclude that low-frequency earthquakes are earthquakes that self-arrest within the rupture patch without any introduced interference. We also explain the scaling property of low-frequency earthquakes. Our findings suggest a framework for fault deformation in which nucleation asperities can release stress through slow self-arrest processes.

报告人：魏雪婷

报告二：2008年5月12日发生于龙门山中央断裂的Mw 7.9汶川地震为逆冲为主的特大大陆灾害地震，造成了几百公里地表破裂和米级的地表位移。龙门山断层系统位于青藏高原的松潘块体与四川盆地的边界，边界地带具有明显的地形地貌差异（即地形梯度陡立）。边界带区域的显著地形地貌差异、活跃的板内特大地震与龙门山推覆构造中的发震断层几何结构以及下覆的中下地壳、上地幔流变结构存在何种动力学关系，成为了近10年来青藏高原东缘的形变机制研究，亟待解决的地球科学问题之一。本文利用三维粘弹性有限元模型研究不同震后形变机制的时空特征，进一步探究了该区域岩石圈和上地幔三维流变结构和性质。本文首先模拟了此次地震的同震地表位移，并与已发表的Okada理论模型预测值进行比较以验证三维有限元力学模型的网格有效性、断层面震源模型的可靠性等。然后，结合已有震后研究中所提供的模型参数的震后形变机制确定较合理的模型分层结构和网格离散模式。最后，利用10年期的震后形变研究了龙门山发震断层震后滑动时空演化，约束了青藏高原东缘的松潘块体、龙门山推覆构造与四川盆地的中下地壳、上地幔的流变性质和横向不均一性，为进一步深入研究青藏高原东缘边界带区域的构造演化机制提供可靠的参考模型。

报告人：陈云锅